I have a optical paper tape reader called a "TPR-1" connected to my Altair. We bought it as a kit. It has a pretty blue box that matches the computer. It uses a standardized part that has phototransistors spaced correctly to read paper tape. The sprocket hole also has a phototransistor that is used as the clock. This is how we always loaded Altair Basic. I saw the manual a few days ago. I'll see if I can scan it. -Rob -----Original Message----- From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]On Behalf Of Andy Holt Sent: Wednesday, November 27, 2002 1:34 AM To: cctalk(a)classiccmp.org Subject: RE: Optical paper tape readers Another problem with building a paper tape reader is to ensure that the light source is constant - in particular that it does not vary with mains frequency! (Memories of getting a PTR modified to work on my homebrew 6800 system 25 years ago) Andy